A well-bore is drilled by driving a rotating drilling bit connected to one end of a drill string into the earth. A continuous flow of pressurized drilling fluid (also known as “drilling mud” or “mud”) supplied through the drill string is used to lubricate and cool the dill bit and other components of the bottom hole assembly (“BHA”). In some drill pipe drilling operations and in all coil tubing drilling (because coil tubing cannot be rotated on its axis), mud is used to drive a mud motor which powers rotation of the drill bit. The inflowing pressurized drilling fluid gets released at the BHA, near the bottom of the continually-lengthening well bore. The continuous inflow of the pressurized drilling fluid pushes the newly-released drilling fluid up the well bore on the outside of the drill string, and back to the surface of the earth.
On its way back to the surface, the drilling fluid carries away loose dirt, pieces of rock (most of which is generated during cutting action of the drill bit), and gases (including trapped gases which were released while drilling and gases which have seeped into the bore from gaseous zones/formations surrounding the bore).
At the surface, the released drilling fluid is filtered and recycled to make it fit for reuse. Though popular (and commercially viable) filtration and recycling methods remove trapped gaseous impurities to an extent, a considerable amount of gases remain trapped and are passed into the drill string during reuse of the recycled fluid.
These trapped gases may cause cavitation or even ‘gas-lock’ in the pumping equipment and reduce the hydrostatic pressure within the drill string. Additionally, since the trapped gases may be flammable (such as methane or natural gas), they pose a risk of fire or explosion if not removed. Still further, some trapped gases, including nitrogen and sulfur gas, can react with and corrode the drilling equipment, including especially flexible seals, O-rings and pump components, including impellers.
For separation of gases trapped in continuously flowing pressurized drilling fluid various gas-separators which are installable in the drill string have been proposed. This invention is a substantial improvement over prior art gas-separators.